Test Driven Development

Question 1

Test Driven Development:

Basic Idea

Answer 1

• Think about what code should do before writing any code
• Write a test for that requirement
• Write the simplest possible code that passes that test, without causing it to fail existing tests
• Refactor code as necessary to pass all tests

The idea is to meet requirements incrementally and always have working code.

This is called the “Red-Green-Refactor” cycle

Question 2

Benefits of

Test Driven Development

Answer 2

• Confidence in Change:
  
  • Increase overall confidence in the code
  • Fearlessly change code
• Provides Documentation of Requirements
• Discover Usability issues early
• Results in high quality software

Question 3

Test Driven Development:

Three Laws

Answer 3

DO NOT write production code until you have written failing unit tests

DO NOT write more of a unit than is sufficient to fail

DO NOT write more production code than is sufficient to pass the currently failing test

Question 4

Test Driven Development:

Most Important Rule

Answer 4

DO NOT

Write code in your head

BEFORE

You write the TEST

Question 5

Test Driven Development

Cycle

Answer 5

Write Test Code (Red)

Write Functional Code (Green)

Refactor

Question 6

TDD Cycle:

Write Test Code (Red) Phase

Purpose and Benefits

Answer 6

• Write a test that fails
• Guarantees all code is testable
• Provides specification for the code that will be written in the next phase
• Helps you think about the design
• Ensures functional code is tangible

Question 7

TDD Cycle:

Write Functional Code (Green) Phase

Purpose and Benefits

Answer 7

• Write the simplest working solution
• Fulfill the requirements of the test code
• Leave improvements/optimizations for later
• Code written is only designed to pass the test

Question 8

TDD Cycle:

Refactor Phase

Purpose and Benefits

Answer 8

• Clean up all code (test and production)
• Make sure code expresses intent
• Rethink/optimize design
• Delete unnecessary code